Trofimov Anton A, Polyakov Konstantin M, Boyko Konstantin M, Tikhonova Tamara V, Safonova Tatyana N, Tikhonov Alexey V, Popov Alexandre N, Popov Vladimir O
Engelhardt Institute of Molecular Biology, Russian Academy of Sciences, ul. Vavilova 32, Moscow 119991, Russia.
Acta Crystallogr D Biol Crystallogr. 2010 Oct;66(Pt 10):1043-7. doi: 10.1107/S0907444910031665. Epub 2010 Sep 18.
The structures of complexes of octahaem cytochrome c nitrite reductase from the bacterium Thioalkalivibrio nitratireducens (TvNiR) with the substrate sulfite (1.4 Å resolution; R(cryst) = 0.126) and the inhibitor cyanide (1.55 Å resolution; R(cryst) = 0.148) have been established. The complex with sulfite was prepared by the reduction of the protein crystal with sodium dithionite. The sulfite ion is bound to the iron ion of the catalytic haem through the S atom. The Fe-S distance is 2.24 Å. The structure of the cyanide complex with full occupancy of the ligand site was established for the first time for cytochrome c nitrite reductases. The cyanide ion is bound to the catalytic haem iron through the C atom. The Fe-C distance is 1.91 Å and the Fe-C-N angle is 171°. The sulfite reductase activity of TvNiR was measured at different pH values. The activity is 0.02 µmol of HS(-) per minute per milligram at pH 7.0; it decreases with increasing pH and is absent at pH 9.0.
